2. Wooden structure

First, the structure of the box should be designed. In the current designs, the structure is made of masonite and each side is a double layer of 1/4 inch wood, glued together using wood glue. The 4 sides have a little indentation on the edges so that when they are closed they match together to create a rectangular shape. In this prototype the wood was cut using a laser cutting machine and here is the file that was submitted to create this shape, to give you a practical example of how the dimensions of the sides of the box should be figured out: scrollableN1_lasercut.zip

3. Rolling mechanism

On one side of the box a rubber wheel produces the kind of friction we need, making it easier to pull the paper. The hole in the middle was made using a 1/4 inch drill bit, so that the wheel can slide easily on a 1/4 inch threaded rod. The wheel comes is the meant to contain a rotary encoder, in the kit that you can find here.

On the other side of the box a piece of round wood will be enough to make the paper slide easily. The round wood also has a hole in the middle, made using the same 1/4 inch drill bit.

4. Rotary encoder

The rotary encoder in the picture has 4 connections: power, ground, input A and input B. The two inputs correspond to the two optical sensors that have to be placed under the white plastic teeth at the center of the wheel.
In order to do so, we have to attach the encoder to the threaded rod, so that it doesn't move independently (only the wheel should move).

The encoder in the picture comes with that white plastic sustain, inside which I put a piece of wood with a little hole in it. The hole was made using a 7/32 drill bit, a little smaller than a 1/4 inch, to make it more firmly attached to the rod.

Finally the encoder can be manually screwed in until it reaches the position at the center of the wheel.

5. Assemble the box

Secure the threaded rods using locking nuts.

Notice how the holes in the side of the box are meant to hold the threaded rods. Those holes are placed at a specific height, which allows the wheel and the round wood to lean out on the top of the surface, so to avoid too much friction between the paper and the surface of the box.

6. Paper

The paper should be pretty robust to survive the constant pulling of different users. The kind of paper used in this example is parchment.

It should be wrapped around the surface of the box and the two rolling mechanisms (the wheel and the round wood). If it is not long enough to cover the entire space, two different stripes of paper can be sewed together.

The last two margins of the paper roll can be connected using tape, creating a closed roll, once the paper has been wrapped around the rolling mechanisms.